1. Field of the Invention
The present invention relates to a solid-state imaging element and a solid-state imaging apparatus, and, in particular, it relates to a Charge-Coupled Device (CCD) type solid-state imaging element and a solid-state imaging apparatus provided with at least two or more charge transfer horizontal shift registers.
2. Related Art
A conventional CCD type solid-state imaging element is generally composed of a plurality of light receiving elements which are arrayed in vertical and horizontal directions on a semiconductor substrate, a plurality of charge transfer vertical shift registers which are arranged adjacent to each of these light receiving elements, and charge transfer horizontal shift registers which are juxtaposed to one end of each of these charge transfer vertical shift registers, and whereby a charge accumulated in each light receiving element in accordance with an incident light is transferred via the vertical shift registers and the horizontal shift registers.
An output amplification circuit is provided at one end of each of the charge transfer horizontal shift registers. The output amplification circuit, which is operable to output a voltage corresponding to a quantity of charge transferred, outputs information of a quantity of charge accumulated in each light receiving element as a voltage signal.
As there is a need for further improvements in functions and operability of a solid-state imaging apparatus provided with such a solid-state imaging element as described above, demands for higher mega-pixels and higher frame rates are increasing for this solid-state imaging element for use in the solid-state imaging apparatus.
In particular, in the case where the solid-state imaging element is made to have enhanced mega-pixels, its frame rate decreases due to an increased number of light receiving elements formed on a semiconductor substrate, thereby impairing the ease of use and operability of the solid-state imaging apparatus since it becomes difficult to shorten imaging intervals, and an upper limit of continuous imaging is suppressed and so on.
Therefore, nowadays, in order to enhance pixel-multiplication of the solid-state imaging elements and at the same time to improve the frame rate, there are attempted for the solid-state element to increase its drive frequency and/or to pluralize output channels of signals to be outputted from the horizontal shift register.
In the case of pluralizing the output channels, charge transfer horizontal shift registers may be provided in a plurality of numbers. More specifically, as shown in FIG. 10, it is practiced that a first horizontal shift register 300a and a second horizontal shift register 300b are disposed facing each other, and interposing therebetween an imaging region 200 in which a plurality of light receiving elements 100 are arrayed in a grid. Refer, for example, to a Japanese Patent Application Publication No. 1996-125158.
A charge transfer vertical shift register which is disposed adjacent to the light receiving elements 100 for transferring a charge accumulated in a light receiving element 100 to a first horizontal shift register 300a or to a second horizontal shift register 300b is provided as many numbers as required within an imaging region 200. And, in particular, in the solid-state imaging element shown in FIG. 10, a first vertical shift register 400a for transferring a charge to the first horizontal shift register 300a and a second vertical shift register 300b for transferring a charge to a second horizontal shift register 300b are disposed alternately.
By arranging as described above so that a signal is enabled to be output from the first horizontal shift register 300a and the second horizontal shift register 300b, the frame rate can be improved. In FIG. 10, 500a denotes a first output amplification circuit provided at one end of the first horizontal shift register 300a, and 500b denotes a second output amplification circuit provided at one end of the second horizontal shift register 300b. 